Image sensors

ABSTRACT

Image sensors are provided. The image sensors may include a plurality of unit pixels and a color filter array on the plurality of unit pixels. The color filter array may include a color filter unit including four color filters that are arranged in a two-by-two array, and the color filter unit may include two yellow color filters, a cyan color filter, and one of a red color filter or a green color filter.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. non-provisional application claims priority under 35 U.S.C §119 to Korean Patent Application No. 10-2018-0002920 filed on Jan. 9,2018, in the Korean Intellectual Property Office, the disclosure ofwhich is hereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure generally relates to an image sensor, and moreparticularly, to a complementary metal oxide semiconductor (CMOS) imagesensor.

Image sensors convert optical images into electrical signals. Recentadvances in the computer and communication industries have led to strongdemand for high performance image sensors in various consumer electronicdevices such as digital cameras, camcorders, PCSs (PersonalCommunication Systems), game devices, security cameras, medicalmicro-cameras, etc.

Image sensors encompass various types, including a charge coupled device(CCD) type and a complementary metal oxide semiconductor (CMOS) type.Operation of CMOS image sensors may be less complicated, and sizes ofCMOS image sensors may be possibly minimized since signal processingcircuits could be integrated into a single chip. CMOS image sensors mayconsume relatively small amount of power and thus may be beneficial inview of battery capacity. In addition, since manufacturing processes ofCMOS image sensors may be compatible with CMOS process technology, theCMOS image sensors may be manufactured with low cost.

SUMMARY

Embodiments of the inventive concept provide image sensors with improvedoptical characteristics.

According to example embodiments of inventive concept, image sensors mayinclude a plurality of unit pixels and a color filter array on theplurality of unit pixels. The color filter array may include a colorfilter unit including four color filters that are arranged in atwo-by-two array, and the color filter unit may include two yellow colorfilters, a cyan color filter, and one of a red color filter or a greencolor filter.

According to example embodiments of inventive concept, images sensor mayinclude a color filter including two yellow color filters, a cyan colorfilter, and a red color filter that are in a two-by-two array:

$\quad\begin{bmatrix}Y & R \\C & Y\end{bmatrix}$

Y represents one of the two yellow color filters, C represents the cyancolor filter, and R represents the red color filter.

According to example embodiments of inventive concept, image sensors mayinclude a substrate including a plurality of photoelectric conversiondevices and a color filter unit on the substrate. The color filter unitmay include four color filters including two first color filters, asecond color filter, and a third color filter that are in a two-by-twoarray:

$\quad\begin{bmatrix}{{first}\mspace{14mu}{color}\mspace{14mu}{filter}} & {{third}\mspace{14mu}{color}\mspace{14mu}{filter}} \\{{second}\mspace{14mu}{color}\mspace{14mu}{filter}} & {{first}\mspace{14mu}{color}\mspace{14mu}{filter}}\end{bmatrix}$

Each of the two first color filters and the second color filter may be acomplementary color filter, and the third color filter may be a primarycolor filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an image sensor according toexample embodiments of the present inventive concept.

FIG. 2 illustrates a circuit diagram of an active pixel sensor array ofan image sensor according to example embodiments of the presentinventive concept.

FIG. 3 illustrates a plan view of a color filter array of an imagesensor according to example embodiments of the present inventiveconcept.

FIGS. 4A and 4B illustrate cross-sectional views respectively takenalong the lines I-I′ and the II-II′ of FIG. 3 according to exampleembodiments of the present inventive concept.

FIG. 5A is a graph showing transmittance characteristics of a primarycolor filter array according to example embodiments of the presentinventive concept.

FIG. 5B is a graph showing transmittance characteristics of acomplementary color filter array according to example embodiments of thepresent inventive concept.

FIG. 6 is a graph showing transmittance characteristics of a colorfilter array according to example embodiments of the present inventiveconcept.

FIG. 7 illustrates a plan view of a color filter array of an imagesensor according to example embodiments of the present inventiveconcept.

FIGS. 8A, 8B, 9A, 9B, 10A, and 10B illustrate cross-sectional views ofan image sensor according to example embodiments of the presentinventive concept.

DETAILED DESCRIPTION

As used herein the term “and/or” includes any and all combinations ofone or more of the associated listed items. It will be understood thatlike reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

It will be understood that “formed concurrently” refers to being formedin a same fabrication step, at approximately (but not necessarilyexactly) the same time.

FIG. 1 illustrates a block diagram of an image sensor according toexample embodiments of the inventive concept.

Referring to FIG. 1, an image sensor may include an active pixel sensorarray (APS) 1, a row decoder 2, a row driver 3, a column decoder 4, atiming generator 5, a correlated double sampler (CDS) 6, ananalog-to-digital converter (ADC) 7, and an input/output (I/O) buffer 8.

The active pixel sensor array 1 may include a plurality oftwo-dimensionally arranged unit pixels, each of which is configured toconvert optical signals into electrical signals. The active pixel sensorarray 1 may be driven by a plurality of driving signals such as, forexample, a pixel select signal, a reset signal, and/or a charge transfersignal that the row driver 3 generate and/or provide. The correlateddouble sampler 6 may be provided with the converted electrical signals.

The row driver 3 may provide the active pixel sensor array 1 withdriving signals for driving unit pixels in accordance with a decodedresult obtained from the row decoder 2. When the unit pixels arearranged in a matrix shape, the driving signals may be supplied torespective rows.

The timing generator 5 may provide the row decoder 2 and the columndecoder 4 with timing and control signals.

The correlated double sampler 6 may receive the electrical signalsgenerated in the active pixel sensor array 1 and may hold and/or samplethe received electrical signals. The correlated double sampler 6 mayperform a double sampling operation to sample a specific noise level anda signal level of the electrical signal and then may output a differencelevel corresponding to a difference between the noise and signal levels.

The analog-to-digital converter (ADC) 7 may convert analog signals,which correspond to the difference level output from the correlateddouble sampler 6, into digital signals and then may output the converteddigital signals.

The input/output buffer 8 may latch the digital signals and then maysequentially output the latched digital signals to an image signalprocessing unit (not shown) in response to the decoded result obtainedfrom the column decoder 4.

FIG. 2 illustrates a circuit diagram showing an active pixel sensorarray of an image sensor according to example embodiments of theinventive concept.

Referring to FIGS. 1 and 2, a sensor array 1 may include a plurality ofunit pixels PX, which may be arranged in a matrix shape. Each of theunit pixels PX may include a transfer transistor TX and logictransistors RX, SX, and DX. The logic transistors may include a resettransistor RX, a select transistor SX, and a drive transistor DX. Thetransfer transistor TX may include a transfer gate TG. Each of the unitpixels PX may further include a photoelectric conversion device PD and afloating diffusion region FD.

The photoelectric conversion device PD may generate and accumulatephoto-charges in proportion to an amount of externally incident light.The photoelectric conversion device PD may include, for example, aphotodiode, phototransistor, a photogate, a pinned photodiode, or acombination thereof. The transfer transistor TX may transfer the chargesgenerated in the photoelectric conversion device PD into the floatingdiffusion region FD. The floating diffusion region FD may accumulativelystore the charges generated and transferred from the photoelectricconversion device PD. The drive transistor DX may be controlled by anamount of photo-charges accumulated in the floating diffusion region FD.

The reset transistor RX may periodically reset the charges accumulatedin the floating diffusion region FD. The reset transistor RX may have adrain electrode connected to the floating diffusion region FD and asource electrode connected to a power voltage V_(DD). When the resettransistor RX is turned on, the floating diffusion region FD may besupplied with the power voltage V_(DD) connected to the source electrodeof the reset transistor RX. Accordingly, when the reset transistor RX isturned on, the charges accumulated in the floating diffusion region FDmay be exhausted and thus the floating diffusion region FD may be reset.The reset transistor RX may include a reset gate RG.

The drive transistor DX may serve as a source follower buffer amplifier.The drive transistor DX may amplify a variation (e.g., change) inelectrical potential of the floating diffusion region FD and output theamplified electrical potential to an output line V_(OUT).

The select transistor SX may select each row of the unit pixels PX thatare to be readout. When the select transistor SX is turned on, the powervoltage V_(DD) may be applied to a drain electrode of the drivetransistor DX. The select transistor SX may include a select gate SG.

FIG. 3 illustrates a plan view of a color filter array of an imagesensor according to example embodiments of the inventive concept.

Referring to FIG. 3, an active pixel sensor array 1 may include colorfilter units FU (i.e., a group of color filters). The color filter unitsFU may be two-dimensionally arranged both in a first direction D1 (e.g.,column direction) and in a second direction D2 (e.g., a row direction).In some embodiments, each of the first direction D1 and the seconddirection D2 may be a horizontal direction, and the first direction D1may be perpendicular to the second direction D2. Each of the colorfilter units FU may include four color filters 303 that are arranged ina two-by-two (2×2) array (i.e., an array having two rows and twocolumns). In some embodiments, the four color filters 303 of a singlecolor filter unit FU may be arranged to form a two-by-two (2×2) array,as illustrated in FIG. 3. In some embodiments, each of the color filterunits FU may include four color filters 303. In some embodiments, eachof the color filter units FU may consist of (i.e., may only include)four color filters 303, as illustrated in FIG. 3. The color filters 303of the color filter units FU may be disposed to correspond to aplurality of unit pixels.

Each of the color filter units FU may include a first color filter 303a, a second color filter 303 b, and a third color filter 303 c. Thefirst and second color filters 303 a and 303 b may be complementarycolor filters, and the third color filter 303 c may be a primary colorfilter. For example, the first color filter 303 a may be a yellow colorfilter, the second color filter 303 b may be a cyan color filter, andthe third color filter 303 c may be a red color filter. Each of thecolor filter units FU may include two yellow color filters Y, cyan colorfilter C, and red color R filter that are arranged in a two-by-two (2×2)array below. In some embodiments, the two yellow color filters Y may beadjacent each other in a diagonal direction (i.e., the third directionD3) with respect to the first direction D1 or the second direction D2 asillustrated in FIG. 3.

$\quad\begin{bmatrix}Y & R \\C & Y\end{bmatrix}$

The first color filter 303 a may be configured to allow yellow visiblelight to pass through, and a unit pixel having the first color filter303 a may generate photo-charges corresponding to the yellow visiblelight. The second color filter 303 b may be configured to allow cyanvisible light to pass through, and a unit pixel having the second colorfilter 303 b may generate photo-charges corresponding to the cyanvisible light. The third color filter 303 c may be configured to allowred visible light to pass through, and a unit pixel having the thirdcolor filter 303 c may generate photo-charges corresponding to the redvisible light.

In some embodiments, each of the first color filter 303 a, the secondcolor filter 303 b, and the third color filter 303 c overlaps a singlecorresponding one of photoelectric conversion regions 110, asillustrated in FIGS. 4A and 4B. In other words, in some embodiments, thefirst color filter 303 a, the second color filter 303 b, and the thirdcolor filter 303 c are in a one-to one relationship with thephotoelectric conversion regions 110, as illustrated in FIGS. 4A and 4B.

A single color filter unit FU may be provided with two first colorfilters 303 a. For example, the first to third color filters 303 a, 303b, and 303 c may be arranged in a Bayer pattern in which the number offirst color filters 303 a is twice the number of second color filters303 b or the number of third color filters 303 c.

In the active pixel sensor array 1, the first color filters 303 a may bearranged in a third direction D3. The third direction D3 may intersectboth the first and second directions D1 and D2. For example, the firstcolor filters 303 a may be adjacent to each other neither in the firstdirection D1 nor in the second direction D2. In the active pixel sensorarray 1, the second and third color filters 303 b and 303 c may bealternately arranged along the third direction D3. Each of the secondand third color filters 303 b and 303 c may be disposed betweenneighboring first color filters 303 a.

In some embodiments, two first color filters 303 a of a single colorfilter unit FU may be arranged along the third direction D3, asillustrated in FIG. 3. The third direction D3 may be a horizontaldirection and may form an angle with the first direction D1 and thesecond direction D2.

FIGS. 4A and 4B illustrate cross-sectional views respectively takenalong the lines I-I′ and II-II′ of FIG. 3 according to exampleembodiments of the inventive concept.

Referring to FIGS. 3, 4A, and 4B, an image sensor according to someembodiments of the inventive concept may include a photoelectricconversion layer 10, a wiring line layer 20, and an opticaltransmittance layer 30. The photoelectric conversion layer 10 may beinterposed between the wiring line layer 20 and the opticaltransmittance layer 30. The photoelectric conversion layer 10 mayinclude a substrate 100 (e.g., semiconductor substrate) andphotoelectric conversion regions 110 provided in the substrate 100. Thephotoelectric conversion regions 110 may convert externally incidentlight into electrical signals. The photoelectric conversion regions 110may generate electrical signals in response to incident light. It willbe understood that the substrate 100 may include a semiconductormaterial. Accordingly, the substrate 100 is referred to as asemiconductor substrate 100 herein. However, it should be noted that asubstrate 100 may include a non-semiconductor material.

The semiconductor substrate 100 may have a first surface 100 a (e.g., afront surface) and a second surface 100 b (e.g., a backside surface)opposite to each other. The wiring line layer 20 may be disposed on thefirst surface 100 a of the semiconductor substrate 100, and the opticaltransmittance layer 30 may be disposed on the second surface 100 b ofthe semiconductor substrate 100. In some embodiments, the first surface100 a of the semiconductor substrate 100 may face the wiring line layer20, and the second surface 100 b of the semiconductor substrate 100 mayface the optical transmittance layer 30.

The wiring line layer 20 may include transfer transistors TX, logictransistors RX, SX, and DX, and first and second wiring lines 212 and213. The transfer transistors TX may be electrically connected to thephotoelectric conversion regions 110. The first and second wiring lines212 and 213 may be connected, through vias VIs, to the transfertransistors TX and the logic transistors RX, SX, and DX. In someembodiments, a single through via VI may extend through a firstinterlayer dielectric layer 221. The wiring line layer 20 may signallyprocess the electrical signals converted in the photoelectric conversionregions 110. The first and second wiring lines 212 and 213 may bedisposed respectively in second and third interlayer dielectric layers222 and 223 stacked on the first surface 100 a of the semiconductorsubstrate 100. In some embodiments, the first and second wiring lines212 and 213 may be arranged regardless of arrangement of thephotoelectric conversion regions 110. For example, the first and secondwiring lines 212 and 213 may cross over the photoelectric conversionregions 110.

The optical transmittance layer 30 may include micro-lenses 307 andfirst to third color filters 303 a, 303 b, and 303 c. The opticaltransmittance layer 30 may focus and/or filter externally incidentlight, and the photoelectric conversion layer 10 may be provided withthe focused and filtered light.

The semiconductor substrate 100 may be, for example, an epitaxial layerformed on a bulk silicon substrate having a first conductivity type(e.g., p-type) that is the same as a conductivity type of the epitaxiallayer. The bulk silicon substrate may be removed from the semiconductorsubstrate 100 in the course of manufacturing an image sensor, and thusthe semiconductor substrate 100 may include only the epitaxial layer ofthe first conductivity type. In some embodiments, the semiconductorsubstrate 100 may be a bulk semiconductor substrate including a well ofthe first conductivity type. In some embodiments, the semiconductorsubstrate 100 may include an epitaxial layer of a second conductivitytype (e.g., n-type), a bulk silicon substrate of the second conductivitytype, a silicon-on-insulator (SOI) substrate, or various substrate.

The semiconductor substrate 100 may include a plurality of unit pixelsPX defined by a first device isolation layer 101. The unit pixels PX maybe two-dimensionally arranged both in a first direction D1 and in asecond direction D2 intersecting each other. For example, the unitpixels PX may be arranged in a matrix shape along the first and seconddirections D1 and D2. When viewed in plan, in some embodiments, thefirst device isolation layer 101 may completely surround each of theunit pixels PX. The first device isolation layer 101 may reduce orpossibly prevent photo-charges generated from light incident onto eachunit pixels PX from randomly drifting into neighboring unit pixels PX.The first device isolation layer 101 may accordingly inhibit or suppresscross-talk phenomenon between the unit pixels PX. In some embodiments,the first device isolation layer 101 may separate the plurality of unitpixels PX from each other. For example, the first device isolation layer101 may separate and/or isolate (e.g., electrically isolate orphysically isolate) the plurality of unit pixels PX from each other.

The first device isolation layer 101 may include an insulating materialwhose refractive index is less than that (e.g., silicon) of thesemiconductor substrate 100. The first device isolation layer 101 mayinclude one or a plurality of insulation layers. For example, the firstdevice isolation layer 101 may include a silicon oxide layer, a siliconoxynitride layer, or a silicon nitride layer.

When viewed in cross-section, the first device isolation layer 101 mayextend from the first surface 100 a toward the second surface 100 b ofthe semiconductor substrate 100. The first device isolation layer 101may penetrate the semiconductor substrate 100, while extending along afourth direction D4. For example, the first device isolation layer 101may have a depth substantially the same as a vertical thickness of thesemiconductor substrate 100. In some embodiments, the first deviceisolation layer 101 may extend completely through the semiconductorsubstrate 100, as illustrated in FIGS. 4A and 4B. In some embodiments,as illustrated in FIGS. 4A and 4B, the first device isolation layer 101may include opposing sides that are spaced apart from each other in avertical direction (i.e., the fourth direction D4) and the opposingsides of the first device isolation layer 101 may be coplanar with thefirst surface 100 a and the second surface 100 b of the semiconductorsubstrate 100, respectively.

The first device isolation layer 101 may have a width that decreases(e.g., gradually decreases) from the first surface 100 a to the secondsurface 100 b of the semiconductor substrate 100. For example, the firstdevice isolation layer 101 may have a first width W1 in the seconddirection D2 adjacent to the first surface 100 a and a second width W2in the second direction D2 adjacent to the second surface 100 b, and thefirst width W1 may be greater than the second width W2.

In some embodiments, the wiring line layer 20, the photoelectricconversion layer 10, and the optical transmittance layer 30 may besequentially stacked in the fourth direction D4, as illustrated in FIG.4A. The fourth direction D4 may be a vertical direction and may beperpendicular to the first, second and third D1, D2, and D3 directions.

The photoelectric conversion regions 110 may be disposed incorresponding unit pixels PX. The photoelectric conversion regions 110may be doped with impurities having the second conductivity type (e.g.,n-type) opposite to a conductive type of the semiconductor substrate100. For example, the photoelectric conversion regions 110 may beadjacent to the second surface 100 b of the semiconductor substrate 100and vertically spaced apart from the first surface 100 a of thesemiconductor substrate 100. Each of the photoelectric conversionregions 110 may include a first region adjacent to the first surface 100a and a second region adjacent to the second surface 100 b, and thefirst region and the second region of the photoelectric conversionregion 110 may have different impurity concentrations. Each of thephotoelectric conversion regions 110 may thus have a potential slopebetween the first surface 100 a and the second surface 100 b.

The semiconductor substrate 100 and the photoelectric conversion regions110 may constitute, for example, photodiodes. In each of the unit pixelsPX, the photodiode may be constituted by a p-n junction between thesemiconductor substrate 100 of the first conductivity type and thephotoelectric conversion region 110 of the second conductivity type.Each of the photoelectric conversion regions 110 constituting thephotodiodes may generate and/or accumulate photo-charges in proportionto magnitude of incident light.

The semiconductor substrate 100 may be provided therein with a seconddevice isolation layer 103 that is adjacent to the first surface 100 aand defines active patterns (i.e., active regions). Each of the unitpixels PX may include the active pattern. For example, the activepattern may include a floating diffusion region FD and an impurityregion DR that are discussed below.

The second device isolation layer 103 may have a width that decreases(e.g., gradually decreases) from the first surface 100 a toward thesecond surface 100 b of the semiconductor substrate 100. The seconddevice isolation layer 103 may have a depth in the fourth direction D4less than a depth of the first device isolation layer 101 in the fourthdirection D4. In some embodiments, the second device isolation layer 103may have a thickness in the fourth direction D4 less than a thickness ofthe first device isolation layer 101 in the fourth direction D4. Thefirst device isolation layer 101 may vertically overlap a portion of thesecond device isolation layer 103. The second device isolation layer 103may include a silicon oxide layer, a silicon oxynitride layer, and/or asilicon nitride layer. For example, the first and second deviceisolation layers 101 and 103 may be integrally connected to each other.

Each of the unit pixels PX may be provided with a transfer transistor(e.g., TX of FIG. 2). The transfer transistor may include a transfergate TG and a floating diffusion region FD. The transfer gate TG mayinclude a lower segment inserted into the semiconductor substrate 100and may also include an upper segment that is connected to the lowersegment and protrudes above the first surface 100 a of the semiconductorsubstrate 100. In some embodiments, as illustrated in FIG. 4A, thetransfer gate TG may include a portion in the semiconductor substrate100 and a portion protruding from the semiconductor substrate 100. Agate dielectric layer GI may be interposed between the transfer gate TGand the semiconductor substrate 100. The floating diffusion region FDmay have the second conductivity type (e.g., n-type) opposite to aconductivity type of the semiconductor substrate 100.

Each of the unit pixels PX may be provided with a drive transistor(e.g., DX of FIG. 2), a select transistor (e.g., SX of FIG. 2), and areset transistor (e.g., RX of FIG. 2). The drive transistor may includea drive gate, the select transistor may include a select gate, and thereset transistor may include a reset gate. Impurity regions DR may beprovided on an upper portion of the active pattern on opposite sides ofeach of the drive, select, and reset gates. For example, the impurityregions DR may have the second conductivity type (e.g., n-type) oppositeto a conductive type of the semiconductor substrate 100.

The second surface 100 b of the semiconductor substrate 100 may beprovided thereon with micro-lenses 307 and first to third color filters303 a, 303 b, and 303 c. Each of the first to third color filters 303 a,303 b, and 303 c may be disposed on a corresponding one of the unitpixels PX. Each of the micro-lenses 307 may be disposed on acorresponding one of the first to third color filters 303 a, 303 b, and303 c. A first planarization layer 301 may be disposed between thesecond surface 100 b of the semiconductor substrate 100 and the first tothird color filters 303 a, 303 b, and 303 c, and a second planarizationlayer 305 may be disposed between the micro-lenses 307 and the first tothird color filters 303 a, 303 b, and 303 c.

The first and second color filters 303 a and 303 b may be complementarycolor filters, and the third color filter 303 c may be a primary colorfilter. For example, the first color filter 303 a may be a yellow colorfilter, the second color filter 303 b may be a cyan color filter, andthe third color filter 303 c may be a red color filter.

Each of the micro-lenses 307 may have a convex shape to focus light thatis incident onto the unit pixel PX. The micro-lenses 307 may verticallyoverlap corresponding photoelectric conversion regions 110. In someembodiments, a single micro-lens 307 may overlap a single photoelectricconversion region 110.

FIG. 5A is a graph showing transmittance characteristics of a primarycolor filter array. Referring to FIG. 5A, a primary color filter arraymay include a red color filter RCF, a green color filter GCF, and a bluecolor filter BCF. The blue color filter BCF may be transparent to bluelight whose wavelength is about 450 nm. The green color filter GCF maybe transparent to green light whose wavelength is about 530 nm. The redcolor filter RCF may be transparent to red light whose wavelength isabout 600 nm. The primary color filter array may be transparent to threeprimary colors of red, green, and blue, thereby achieving relativelyexcellent sharpness. In contrast, the primary color filter array maydecrease pixel sensitivity.

FIG. 5B is a graph showing transmittance characteristics of acomplementary color filter array. Referring to FIG. 5B, a complementarycolor filter array may include a cyan color filter CCF, a magenta colorfilter MCF, and a yellow color filter YCF. Cyan, magenta, and yellowcolors may respectively have a complementary relationship with red,green, and blue colors, i.e., the three primary colors. The cyan colorfilter CCF may be transparent to cyan light whose wavelength fallswithin a range from about 400 nm to about 550 nm. The yellow colorfilter YCF may be transparent to yellow light whose wavelength fallswithin a range from about 500 nm to about 650 nm. The magenta colorfilter MCF may be transparent to magenta light whose wavelength fallswithin a range from about 450 nm to about 600 nm. The magenta colorfilter MCF may be opaque to green light whose wavelength is about 530nm.

The complementary color filter of FIG. 5B may transmit light whosewavelength range is wider than that of light passing through the primarycolor filter array of FIG. 5A. The complementary color filter array mayaccordingly have pixel sensitivity superior to that of the primary colorfilter array. In contrast, the complementary color filter array may havesharpness less than that of the primary color filter array.

FIG. 6 is a graph showing transmittance characteristics of a colorfilter array according to example embodiments of the inventive concept.Referring to FIG. 6, a color filter array according to exampleembodiments of the inventive concept may include two complementary colorfilters (e.g., cyan and yellow colors) and one primary color filter(e.g., red color). The color filter array of the inventive concept maytransmit light whose wavelength range is wider than that of lightpassing through the primary color filter array of FIG. 5A. The colorfilter array according to example embodiments of the inventive conceptmay accordingly have pixel sensitivity superior to that of the primarycolor filter array. The color filter array of the inventive concept mayexactly transmit red light, compared to the complementary color filterarray of FIG. 5B. The color filter array of the inventive concept maytherefore have sharpness greater than that of the complementary colorfilter array.

FIG. 7 illustrates a plan view of a color filter array of an imagesensor according to example embodiments of the inventive concept. Adetailed description of technical features repetitive to those discussedabove with reference to FIG. 3 may be omitted, and differences will bediscussed in detail. Referring to FIG. 7, each of the color filter unitsFU may include two first color filters 303 a, a second color filter 303b, and a third color filter 303 c. The third color filter 303 c may be agreen color filter.

FIGS. 8A, 8B, 9A, 9B, 10A, and 10B illustrate cross-sectional views ofan image sensor according to example embodiments of the inventiveconcept. FIGS. 8A, 9A, and 10A illustrate cross-sectional views takenalong the line I-I′ of FIG. 3, and FIGS. 8B, 9B, and 10B illustratecross-sectional views taken along the line II-II′ of FIG. 3. A detaileddescription of technical features repetitive to those discussed abovewith reference to FIGS. 3, 4A, and 4B may be omitted, and differenceswill be discussed in detail.

Referring to FIGS. 3, 8A, and 8B, the first device isolation layer 101may have a width that gradually increase from the first surface 100 atoward the second surface 100 b. The first device isolation layer 101may have a first width W1 adjacent to the first surface 100 a and asecond width W2 adjacent to the second surface 100 b, and the secondwidth W2 may be greater than the first width W1.

Referring to FIGS. 3, 9A, and 9B, the first device isolation layer 101may have a constant width regardless of a depth of the first deviceisolation layer 101. In some embodiments, the first device isolationlayer 101 may have a uniform width in a horizontal direction (e.g., thesecond direction D2) along a vertical direction (e.g., the fourthdirection D4), as illustrated in FIG. 9A. The first device isolationlayer 101 may have a first width W1 adjacent to the first surface 100 aand a second width W2 adjacent to the second surface 100 b, and thefirst and second widths W1 and W2 may be substantially the same as eachother. For example, a difference between the first and second widths W1and W2 may be less than 3%, 5%, 10% or 15% of the first and secondwidths W1 and W2.

Referring to FIGS. 3, 10A, and 10B, the photoelectric conversion layer10 may include a semiconductor substrate 100 and first and secondphotoelectric conversion regions 110 a and 110 b that are provided inthe semiconductor substrate 100. The first and second photoelectricconversion regions 110 a and 110 b may convert externally incident lightinto electrical signals. A pair of first and second photoelectricconversion regions 110 a and 110 b may be provided in each of the unitpixels PX. Each of the first and second photoelectric conversion regions110 a and 110 b may be doped with impurities having the secondconductivity type (e.g., n-type) opposite to a conductivity type of thesemiconductor substrate 100.

Each of the first and second photoelectric conversion regions 110 a and110 b may include a first region adjacent to the first surface 100 a anda second region adjacent to the second surface 100 b, and the first andsecond regions have different impurity concentrations. Each of the firstand second photoelectric conversion regions 110 a and 110 b may thenhave a potential slope between the first and second surfaces 100 a and100 b of the semiconductor substrate 100.

The semiconductor substrate 100 and the first and second photoelectricconversion regions 110 a and 110 b may constitute a pair of photodiodes. In each of the unit pixels PX, the pair of photodiodes may beconstituted by p-n junctions between the semiconductor substrate 100 ofthe first conductivity and the first conversion region 110 a and betweenthe semiconductor substrate 100 of the first conductivity and the secondphotoelectric conversion region 110 b of the second conductivity.

In each of the unit pixels PX, a difference in phase (e.g., phase offsetor phase difference) may be provided between an electrical signal outputfrom the first photoelectric conversion region 110 a and an electricalsignal output from the second photoelectric conversion region 110 b. Inan image sensor illustrated in FIGS. 10A and 10B, correction in focusmay be performed by comparing the difference in phase between theelectrical signals output from a pair of the first and secondphotoelectric conversion regions 110 a and 110 b.

In each of the unit pixels PX, a third device isolation layer 105 may bedisposed between the first and second photoelectric conversion regions110 a and 110 b. When viewed in plan, the third device isolation layer105 may include a first part P1 extending in the first direction D1while running across one unit pixel PX and a second part P2 extending inthe second direction D2 while running across the one unit pixel PX. Forexample, the third device isolation layer 105 may have a cross shape ina plan view. The first part P1 of the third device isolation layer 105may be disposed between the first and second photoelectric conversionregions 110 a and 110 b. The second part P2 of the third deviceisolation layer 105 may run across the first and second photoelectricconversion regions 110 a and 110 b. The third device isolation layer 105may extend from the second surface 100 b toward the first surface 100 aof the semiconductor substrate 100. The third device isolation layers105 may be spaced apart from the first surface 100 a of thesemiconductor substrate 100. In some embodiments, the third deviceisolation layers 105 may not extend through the semiconductor substrate100 and thus may be vertically spaced apart from the first surface 100 aof the semiconductor substrate 100 as illustrated in FIGS. 10A and 10B.

In some embodiments, the first device isolation layer 101 and the thirddevice isolation layer 105 may be formed at the same time (e.g.,concurrently). In some embodiments, the third device isolation layer 105may include the same insulating material as that of the first deviceisolation layer 101. The third device isolation layer 105 may beintegrally connected to the first device isolation layer 101. In someembodiments, the third device isolation layer 105 and the first deviceisolation layer 101 may have a unitary structure, and an interfacebetween the third device isolation layer 105 and the first deviceisolation layer 101 may not be visible.

The third device isolation layer 105 may reduce or possibly preventcross-talk between the first and second photoelectric conversion regions110 a and 110 b in each of the unit pixels PX. Accordingly, each of theunit pixels PX may be configured to detect (e.g., exactly detect) aphase difference of an electrical signal. As a result, an image sensoraccording to some embodiments of the inventive concept may have anincreased auto-focusing function.

According to inventive concept, an image sensor may have pixelsensitivity superior to that of a primary color filter array including(e.g., consisting of) red, green, and blue colors. Also, the imagesensor may have sharpness (e.g., image sharpness) superior to that of acomplementary color filter array including (e.g., consisting of) cyan,magenta, and yellow colors.

Although example embodiments of the inventive concept have beendiscussed with reference to accompanying figures, it will be understoodthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the inventive concept. Ittherefore will be understood that the embodiments described above arejust illustrative, not restrictive, and the appended claims are intendedto cover all such modifications, enhancements, and other embodiments,which fall within the true spirit and scope of the inventive concept.Thus, to the maximum extent allowed by law, the scope is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

What is claimed is:
 1. An image sensor comprising: a plurality of unitpixels; and a color filter array on the plurality of unit pixels,wherein the color filter array comprises a color filter unit comprisingfour color filters that are arranged in a two-by-two array, and whereinthe color filter unit comprises two yellow color filters, a cyan colorfilter, and a red color filter.
 2. The image sensor of claim 1, whereina first row of the two-by-two array of the color filter unit comprisesthe cyan color filter and a first one of the two yellow color filters,and wherein a second row of the two-by-two array of the color filterunit comprises a second one of the two yellow color filters that isadjacent to the first one of the two yellow color filters in a diagonaldirection with respect to a row direction.
 3. The image sensor of claim1, wherein the color filter unit comprises a plurality of color filterunits that comprises a plurality of yellow color filters, a plurality ofcyan color filters, and a plurality of red color filters, and whereinthe plurality of yellow color filters, the plurality of cyan colorfilters, and the plurality of red color filters of the plurality ofcolor filter units are in a Bayer pattern.
 4. The image sensor of claim1 further comprising a substrate comprising a first surface and a secondsurface opposite the first surface, wherein each of the plurality ofunit pixels comprises a photoelectric conversion region in thesubstrate, and wherein the first surface of the substrate faces thecolor filter array.
 5. The image sensor of claim 4, wherein thesubstrate has a first conductivity type, and wherein the photoelectricconversion region of each of the plurality of unit pixels has a secondconductivity type different from the first conductivity type.
 6. Theimage sensor of claim 4, wherein each of the plurality of unit pixelsfurther comprises a plurality of transistors on the second surface ofthe substrate.
 7. The image sensor of claim 4 further comprising adevice isolation layer in the substrate, wherein the device isolationlayer isolates the plurality of unit pixels from each other.
 8. Theimage sensor of claim 7, wherein the first surface and the secondsurface of the substrate are spaced apart from each other in a verticaldirection, and wherein the device isolation layer has a first width in ahorizontal direction adjacent to the first surface of the substrate andhas a second width in the horizontal direction adjacent to the secondsurface of the substrate, and the first width is different from thesecond width.
 9. An image sensor comprising: a color filter unitcomprising two yellow color filters, a cyan color filter, and a redcolor filter that are in a two-by-two array: $\quad\begin{bmatrix}Y & R \\C & Y\end{bmatrix}$ wherein Y represents one of the two yellow color filters,C represents the cyan color filter, and R represents the red colorfilter.
 10. The image sensor of claim 9, wherein the color filter unitcomprises a plurality of color filter units that are arrangedtwo-dimensionally.
 11. The image sensor of claim 9, wherein the colorfilter unit comprises a plurality of color filter units that comprise aplurality of yellow color filters, a plurality of cyan color filters,and a plurality of red color filters, and wherein the plurality ofyellow color filters, the plurality of cyan color filters, and theplurality of red color filters of the plurality of color filter unitsare in a Bayer pattern.
 12. The image sensor of claim 9, furthercomprising a plurality of unit pixels arranged in a two-by-two array,wherein each of the plurality of unit pixels is in one-to-onerelationship with one of the yellow color filters, the cyan colorfilter, or the red color filter of the color filter unit, wherein eachof the plurality of unit pixels comprises: a photoelectric conversiondevice; a transfer transistor configured to control transfer of chargesgenerated in the photoelectric conversion device; and a floatingdiffusion region configured to receive the charges.
 13. The image sensorof claim 12, further comprising a substrate, wherein the photoelectricconversion device comprises a photoelectric conversion region in thesubstrate, wherein the substrate has a first conductivity type, andwherein the photoelectric conversion region has a second conductivitytype that is different from the first conductivity type.
 14. An imagesensor comprising: a substrate including a plurality of photoelectricconversion devices; and a color filter unit on the substrate, whereinthe color filter unit comprises four color filters that comprise twofirst color filters, a second color filter, and a third color filterthat are in a two-by-two array: $\quad{\begin{bmatrix}{{first}\mspace{14mu}{color}\mspace{14mu}{filter}} & {{third}\mspace{14mu}{color}\mspace{14mu}{filter}} \\{{second}\mspace{14mu}{color}\mspace{14mu}{filter}} & {{first}\mspace{14mu}{color}\mspace{14mu}{filter}}\end{bmatrix},}$ wherein each of the two first color filters and thesecond color filter is a complementary color filter, and wherein thethird color filter is a primary color filter that is a red color filter.15. The image sensor of claim 14, wherein colors of the second and thirdcolor filters have a complementary relationship with each other.
 16. Theimage sensor of claim 14, wherein each of the two first color filters isa yellow color filter, and the second color filter is a cyan colorfilter.
 17. The image sensor of claim 14, wherein the color filter unitcomprises a plurality of color filter units, and wherein the first,second and third color filters of the plurality of color filter unitsare in a Bayer pattern.
 18. The image sensor of claim 14, wherein eachof the first, second and third color filters overlaps a respective oneof the plurality of photoelectric conversion devices.
 19. The imagesensor of claim 14, wherein each of the first, second and third colorfilters overlaps a pair of the plurality of photoelectric conversiondevices.
 20. The image sensor of claim 14, wherein each of the pluralityof photoelectric conversion devices comprises a photoelectric conversionregion in the substrate, wherein the substrate has a first conductivitytype, and wherein the photoelectric conversion region has a secondconductivity type that is different from the first conductivity type.